You can try selecting a sequence key and copy/pasting it back into a sequence. Anim8or will ask if you want to convert the sequence keys into ordinary keys. Click ok. You've still got the keys showing, but they can now be deleted as per normal keys. (use 'cut') To select a block of normal keys , select the first to be deleted, hold shift and click the last. It would actually be a good thing to have a 'delete sequence' option tho.